A constellation’s footprint

We’re going away on Thursday for a few sunny days near the Tropic of Cancer.  I’m a bit sheepish, because we keep resolving never to get into another airplane.  So I’ll make a mystery of it – make you a small astronomical-cum-geographical riddle to solve, like the “Forbidden Island” one of three years ago.

Think of the Greek capital letter Pi, which looks like two legs with a bar across the top.  Slant it so that it tips to the left.  There is a constellation shaped like that – two parallel lines, sloping from northeast to southwest, roughly from declination 30 down to 20 north.

There is also a pair of long thin geographical features on our planet, parallel to each other and sloping the same way, from northwest to southeast, also roughly from latitude 30 to 20 north.

(Northeast to southwest, northwest to southeast – are those the same directions of slope?  Yes, because you look up at the sky and down at the Earth.)

So when the constellation passes overhead of the geographical formation, they overlie, or mirror, each other.  If you could look down through the constellation, you’d see it printed over the geographical pair.  That image doesn’t work very well, since the stars are at such huge and various distances, so let’s try another: it’s as if the piece of geography is a rug on a floor, reflected in a mirror in the ceiling.

As the constellations pass overhead, this overlying happens at about sidereal time 7 hours, which, at this time of year, is an hour or so after local midnight.

We won’t be flying to the constellation, but to a bay at the southern end of the geographical formation.

And another clue – and another reason, sort of, for going there – is that this bay is a few miles along the same bit of mountainous coast from a similar though smaller bay from which I and a company of others watched the great eclipse of 1991.  For some, that may make the geographical part of the puzzle too easy.

And a clue that may do the same for the astronomical part:  On the penultimate night before we come back, we should be able to watch, from this beach, the meteors that fall all night from this constellation.  Sparks falling from the mirror to the rug, about vertically.

Meanwhile, here is the Moon rising this evening.

It was Full yesterday, Sunday Dec. 3, at about 16 Universal Time (10 AM Central Standard Time), and at perigee today at 9 UT (3 AM), and as perigee was so close to the Full moment it was the second-nearest perigee of the year (after that of May 26), and you may experience very high tides, though not if you are in the Central time zone.


8 thoughts on “A constellation’s footprint”

  1. We returned a month ago from a stay in New Zealand. I enjoyed very much the extremely dark skies, like none I have seen in the US. (We were in the sparsely populated south of the South Island.) And seeing the Large and Small Magellanic Clouds and the Southern Cross. But the greatest excitement and delight, was seeing the Orion constellation. I first saw the belt without realizing its significance but the positioning and spacing made me curious. Peering up and down I was amazed to see all of Orion, how clear it showed in the dark skies, how sharp the colors of red Betelgeuse and blue Rigel, but most amazing, that it was upside down to my normal viewing in the northern hemisphere. I was definitely not home.

    Traveling is great! Enjoy your trip.

  2. Gemini and Baja California? I would assume that a bay on its western coast would be similar to a bay in the Puerto Vallarta area?

  3. Wow! This post is just FULL* of points to which I can’t all reply to here, but most of all, have a great trup. Earthly objects reflecting celestial ones remind me of the great Pyramids of Egypst and the stars of Orion’s belt. Ancient alien astromers love to bring that up. Thanks for reminding us of the Gemind’s meteor shower stemming from, not a comet, but from some burned out asteroid, Phaethon. I once ate many morning glory seed to observe them when my brother and father arrived at my house and a glance to my bro showed some sort of deja vu moment which he certainly felt too. Mention of the great eclipse of 1991 brings to mind the connections I’ve made with some guys from Europe.(I hope they’re reading this comment now).
    *yes, pun intended for that full supermoon we just had.
    Too many other things to bring up right now, but I’ll be back.
    Again, Have a great trip and holiday season.

  4. I had the constellation figured out before the later clues. The geography clue gives me a general idea where you will be, but not close enough to deliver a package. ¡Buen viaje!

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